# Review validation help

Non-technical explanations for the most common errors and warnings shown during invoice review.

## Review validation help

Non-technical explanations for the most common errors and warnings shown during invoice review.

## Articles

- [Missing required invoice information](/resources/review-validation/missing-required-invoice-information): Required seller, buyer, invoice, currency, and line data.
- [Buyer reference and Leitweg-ID problems](/resources/review-validation/buyer-reference-and-leitweg-id): Routing references for German public-sector XRechnung invoices.
- [Payment and IBAN problems](/resources/review-validation/payment-and-iban-problems): Payment instructions, IBAN format, and bank transfer requirements.
- [VAT, reverse charge, and tax category problems](/resources/review-validation/vat-reverse-charge-and-tax-category-problems): Tax category, exemption, VAT ID, and reverse charge checks.
- [Totals, rounding, and line amount mismatches](/resources/review-validation/totals-rounding-and-line-amount-mismatches): How validators recalculate totals and why amounts may fail.
- [Prepayments and previously paid amounts](/resources/review-validation/prepayments-and-previously-paid-amounts): Deposits, advance payments, and amount-due calculations.
- [Line item and unit code problems](/resources/review-validation/line-item-and-unit-code-problems): Line descriptions, quantities, unit codes, prices, and service periods.
- [ZUGFeRD and Factur-X PDF warnings](/resources/review-validation/zugferd-facturx-pdf-warnings): Hybrid PDF/XML review, stale validation, and source PDF readiness.